Vertical flow process for in situ retorting of oil shale



Sept. 26, 1961 v. D. ALLRED 3,001,775

VERTICAL FLOW PROCESS FOR 1N sm RETORTING OF OIL SHLE Filed Deo. 8, 1958 INVENTOR. VICTOR D. ALLRED ATTQRNEYS.

" through the V\Another object of my invention is to provide a simple United States Patent Victor D.

This invention relates to a process for surface recovery of petroleum constituents evolved byrin situ combustion in underground, petroleum-bearing oil shale formations.V

The present invention has particular application but is not limited to working oil shale formations which are not suited for conventional mining methods and surface retort procedures. For example, a large area of the rich Colorado oil shale deposit is located under an overburden on the order of 1,000 feet and is atsuch a distance from the escarpment that it cannot be economically exploited by conventional techniques. Some of this area has a more or less continuous thickness of shale averaging 25 gallons of oil per ton of shale for a 1,000 foot or greater interval.

Considerable oil can be recovered from such a formation by the use of unit developed according to the present invention with an effective combustion diameter of 100 feet would be expected to yield 330 barrels of shale per foot, or 333,000 barrels per thousand feet. The practice of my invention may utilize certain features of the process disclosed in the co-pending application of Poettmann et al., Serial No. 753,043, filed August 4, 1958 for In Situ Retorting of Oil Shale, assigned to the assignee of this application, and features disclosed but not claimed herein have been claimed in said application.

ln the conventional retorting of oil shales mining and handling expenses for these deep deposits place an excessive cost on the shale oil product and the oil recovery value is not high enough to absorb all Vsuch expense and yield a profit. In addition, the requirement of disposing of the residue solids of a surface retort operation is another factor complicating such processing.

The present invention represents a departure from other methods of in situ retorting in being able to condition a large tonnage of shale for combustion by inexpensive and effective methods. This conditioning permits a selective control of heat front movement and may include the reverse combustion practice described in said application, Serial No. 753,043. It also permits a progressive working lengthwise or laterally of the deposit with little change in surface installations. As heat losses are almost non-existent, proper control of the air permits utilization of optimum combustion effects over long periods of operation with a resulting higher oil recovery.

It is an object of this invention to provide a simple, economical and eflicient process for subjecting a large tonnage of oil shale to in situ retorting under substantially optimum conditions in a progressive operation vertical extent of the shale deposit.

and efficient method of increasing the permeability of the working preparatory retorting operations.

A further object of this invention is to provide a simple, economical and efficient control of combustion in in situ retorting operations.

The practice of the invention will be readily understood by reference to the accompanying drawings. vIn the drawings:

FIG. 1 is a schematic representation, similar to a vertical section, of one type of installation utilizing features of my invention and indicating flows in the workings; and FIG. 2 is another schematic representation similar to in situ retorting. 'For example, a`

to initiating combustion in in situv ment of the retorting countercurrent air circulation is Patented Sept. 26, 1961 FIG. 1, and illustrating another form of flow pattern utilizing features of my invention.

Referring first to FIG. 1, the first phase of the operation will be to drill one or a plurality of holes 3 from the surface 4 through the overburden 5 and the depth of the shale from its top 6 to its bottom is hollowed out at the base of the formation by first fracturing and then dissolving away the shale with an acid solvent, the inorganic content of the shale having an appreciable quantity (21 to 47% cium and magnesium carbonates. Other suitable chemical techniques may be used for dissolution of the rock. Mechanical techniques, such as use of explosives or direct mining are applicable, or a combination of chemical and mechanical techniques may be utilized. The size of cavern 8 will be determined by the void space requireoperation.

Upon completion of the cavern 8, the holes 3 are sealed a short distance above the top of the with explosive which, when detonated, will cause the shale to fracture and cave into the cavern, leaving a roughly cylindrical zone extending vertically through the shale, which is in a loose and permeable condition as a result of the caving. Other fracturing methods may be employed such as hydraulic fracturing or electric fracturing, but explosive fracturing appears to be bestl when an area of substantial diameter is to be Worked.

Following the shale fracturing, the formation is drilled again to provide one or a plurality of holes extending to the base of the fractured shale. Whenever it may be undesirable to drill holes through the fractured shale, an offset well 31 will be drilled through an unfractured portion of the formation and then whipstocked into the bottom of the fractured area 18. In such event, a concentrically lined casing would not be used, and no coolant would be required as well 31 would be entirely out of the hot zone.

As shown in FIG. l, a casing 9 is run from the surface 4 to the top 6 of the fractured zone. Interiorly of this casing, an innermost liner or conduit 11 and an intermediate liner 12 extend from the surface 4 to the bottom 7 of the shale formation. Air or other gases or fluids are supplied from a source (not shown) through a header 13 into the annular space 14 between casing 9 and liner 12, and are injected into the shale formation to support and control the in situ combustion.

' A suitable coolant, such as water, is introduced through another header or conduit 15 into the annular space 16 between liners 11 and 12 Aand is circulated at a rate sufficient to keep liner 12 from collapsing in the hot zone of the combustion front 17. The products of combustion, coolant and shale oil are drawn into and conducted upwardly through conduit 11 to a collection system on the surface (not shown).

In either of the treatments shown in FIGS. l and 2, combustion is initiated in the shale by any suitable method, such as by using an electric heater, disposed at the starting end of the combustion zone, or by preheating of injected air, or by chemical means, or by using a torch. After a temperature on the order of 700 yF. is developed, the heat front begins its progressive vertical movement and by controlling air ilux optimum combustion can be maintained. Evolved products of the combustion drain'through the fractured shale 18 by gravity and the overburden 5 provides Aadequate insulation so that the heat generated by the combustion is utilized in transforming the solid organic matter (kerogen) into a liquid which distills away from the shale, leaving the pyrolyzed or spent shale 19 highly porous and permeable to the ow of the air injected to support combustion. Where provided, as in FIG. 2,

7. A cavern 8V by weight) of calthe increase in permeability adds Ito the eiliciency of the operation.

When the offset well 31 is utilized in an operation of the type shown in FIG. l, one or a plurality of casings'9 will extend downwardly to the shale formation and function as the injection wells, while well 31 will be-connected as the production well to deliver `the evolved products to the surface installation.

FIG. 2 represents a similar installation in which the initial conditioning procedure is the same as previously described in which one or more holes are drilled to form the cavern 8, the shale formation is shattered to form the cylindrical zone, new holes are drilled, and the casing 9 with innermost liner or conduit 11, and intermediate liner 12 are arranged and installed as previously described.

However, in this type of operation, combustion is inited adjacent bottom 7, and initially air may be injected through passage 16 or conduit 11 until the heat front 17 begins its ascending movement away from bottom 7. Then, air supply to the bottom of the hole is cut off and air injection continues through passage 14. Evolved products of the combustion drain through the spent shale tion gases and the shale oil.

In an operation of this type, the reverse combustion procedure is particularly effective in increasing permeability of the spent shale. If the production Well in such an operationis an offset well, such as shown at 31 in FIG. 1, itwill'be unnecessary to use a coolant.

The circuiting shown in FIG. 2 may electively utilize the reverse combustion action described in Serial No. 753,043. Referring to FIG. 2, after the heat front'17 moves to the top 7 of the shale formation, its movement can be reversed by continuing the injection of air through header 13 and passage 14. The pyrolyzed shale-after being subjected to the initial extraction by countercurrent heat front movement contains suliicient combustible matter to support a reverse or cocurrent movement of the heat zone. The shale, as a result of the first extraction, being much more permeable and porous, allows the residual shale oil to drain away from the heat front as it travels to the intake of conduit 11 with little redeposit or retention in the spent shale.

Another method for preparing the oil shale deposit for combustion is to drill one hole to the bottom of the deposit, set casing down' through the formation to the bottom and then fill the casing with mud or some other substance capable of preventing its collapse during the caving operation. Upon completion of the fracturing or caving of the formation, the casing is drilled out to permit its use as the production well.

Under some conditions it may Ybe desirable to have the intake of the production well at the top of the shale formation, as when oil mists are readily produced `by the heat front. In such an operation air usually will be introduced at the bottom, and the heat front movement can be directed either as an ascending movement or a descending movement. Whenever casing of a production well or an injection well extends through the combustion zone, coolant circulation will be utilized to prevent damage to the casing,

In the preceding description, reference has been made to drilling holes through the formation. While this is a preferred practice, it will be understood that holes required in the operation may be produced by methods other Vthan drilling, regular shaft sinking practices being an example. Similarly, the area being worked usually will be cylindrical as previously described, 4but may be otherwise shaped, such as a cube, or pyramid for example. Consequently, where such terms are employed in this specification they are intended to have their broadest connotations and include known equivalents.

The procedures illustrated and described herein are in- 4L tended as typical examples of the practice on my invention and not to limit same, the scope of the invention being set forth in the hereunto appended claims.

I claim:

l. The method of in situ retorting of oil shale deposits, which comprises forming at least one hole through the vertical extent of an oil shale formation, forming a void of substantial vertical extent exteriorly of said hole at the bottom of the shale formation by dissolving formation materials with a solvent, caving the shale overlying said void throughout the vertical extent of the deposit, thereby increasing permeability throughout a substantial portion of the caved shale and substantially 'lling said one end of said permeable por- 3. 'I'he method 5. The method of in situ retorting of oil shale deposits, which comprises forming at least one hole exaxiomes o caving shale overlying said cavern after material removal shale formation, forming a cavern encompassing saidV so as to fall loosely into said cavern, thereby forming hole at the base of said formation and of substantial vervoids increasing permeability in the loosened shale and tical extent by removal of material therefrom, caving defining a retort Zone above said oavorn, initiating ooinshale overlying said cavern after material removal so as bustion at the bottom of said loosely iilled cavern area to fait lOoSoly into Said Cavern, thereby forming VOds with gas introduced at the top of said retort zene for increasing permeability in tho loosened Shale and defining the Support of combustion therein, thereby inducing an a retort zone above said cavern, initiating combustion elevating combustion front movement through said zone at One ond 0f Sad retort ZOB@ With gas introduced at t11e with educed oil draining through the pyroiyzod Shale opposite end thereof for the support of combustion therefollowing passage of the front, and withdrawing evolved l0 in, thereby inducing 2l PI'OgeSSVe Combustion front move' products of the combustion and educed oil from the botment thtlmgh Said Zone Countefcuffellt t0 the gas OW tom of said retort zone through a passage extending to therein With @duced Oil moving through the PYIOlYzed.. the surface. shale in the gas iiow following passage of the front, and 6. The method of in sito reim-ting of oil shale do withdrawing evolved products of the combustion and posits, which comprises lforming at ioast one hole oxtond educed oil from an end of said zone through a passage ing from the surface through the vertical extent cf an oil t0 the Surfaceshale =formation, forming a cavern encompassing said'- 9 A method as defined in Claim 3, in Which a heathole at tho base of Said formation and of Substantial voo insulated passage extends through the combustion zone tical extent by removal of material therefrom, caving to the surface for the removal of evolved products of shale overlying said cavern in a gonorauy Cylindrical 2o combustion and educed oil from the retort zone. pattern after material removal so as to fall loosely into 110 A method as dened in daim 3, in Which the gas said eavern, thoroby forming voids increasing perme introduced and evolved products are passed through a ability in the loosened shale and defining a cylindrical cfmmon bore m sepfa HOY/S Pd a Coolant medium s retort zone above said cavern, initiating combustion at circulated between Sad OWS m, Sald b ofe' the |bottom of said loosely lled cavern area with gas nu A method as defined 111 Clalm 8 m Whch the troduced at the top of said retort zone for the support of evflv'd Products tre Passed t0 tho Surface through a concombustion therein, thereby inducing an elevating comdut dlspsed Outslde the comiusuo? Zone;

bustion front movement through said zone vw'th educed 12. A method as dened m 61mm 8 m Whlch a coni' oil draining through the pyrolyzed Shale following Pas bustron front temperature o n the order of 700 F. 1s sage of the front, and withdrawing evolved pro-ducts of established to eiect oil eduction in the residual shale after the combustion Iand educed oil from the bottom of said passage of the from thrfmgi the retqrt Zone'. retort zone through a passage extending to the surface. 13' The method of m Slm retomng of on Shale de' 7' The method of in Situ retorting of on Shale deposits posits, which comprises forming at least. one hole extendmg from the surface through the vertical extent of an which comprises forming at least one hole extending lfrom the Surface through the Vertical extent of an ou 3a oil shale formation, forming aucavern encompassing sald Shale formation, forming a Cavern encompassing Said. h ole at the base of said formatlon and of substantial verhole at the base of said formation and of substantial vermal extent .by rmoval of mammal therefrom Cavmg tical extent by introducing a solvent into the shale at the Shale overlylflg .Sald cavern after mammal remoyal 5.as bottom of said hole capable of dissolving the inorganic to fau.10osey mm. .Saldi eavem thereby forming Volds content of the shale, caving shale overlying said cavern 40 tncreasmg Permeablhty m the loosened Stvalfi and den' so as to fall loosely into said cavern after material re- .lg a retort Zone abqve Sad cavern .lmtlatmg combus moval by solvent action, thereby forming voids increasnon at the top of s md retort Zone Wlth gas Introduced ing permeability in the loosened shale and defining a reait me bottom of sald. zone for the Supprt of combils' tort zone above said cavern, initiating combustion at the non theem thereby mducng a progressive combustlon bottom of said loosely filled cavern area with gas introfom movement thrugh Sald zon? couniercurrem to the duced at the top of said retort zone for the support of gas ow therem. Wlth edud O11 mfvmg through 'die combustion therein, thereby inducing an elevating compyolyzed shle m the gas 0W fOllOWlng passage of said bustion front movement through said zone with educed fiom and Wlthdralwmg evolved producfs of the combus' ou draining through the pyrolyzed Shale following pw 5o tion and educed oil from the top of said zone through a ge of 1tahe front, and withdrawing evolved products of passage to the sur ace' e com ustion and educed oil from the bottom of said s retort zone through a passage extending to the surface. References Cited m the me of this Patent 8. The method of in situ retorting of oil shale deposits, UNITED STATES PATENTS which comprises forming at least one hole extending 1,919,636 Karrick July 25, 1933 from the surface through the vertical extent of an oil 2,874,777 Tadema Feb. 24, 1959 

